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本工作在室温下采用累积叠轧工艺对纯铜薄板进行1~9道次的大塑性变形加工。采用金相显微镜、双束系统FIB/SEM、TEM及拉伸试验机进行组织观察及力学性能测试,获得纯铜板累积叠轧过程显微组织演变和力学性能演变规律。结果表明:累积叠轧形成的初始界面存在微缝隙和纳米层等缺陷,其中微缝隙随着叠轧的进行而逐渐消失,最终形成冶金界面结合;纳米层由片层厚度为20~60nm的片层晶组成,并包含变形孪晶。在轧辊压缩力与剪切力的共同作用下,原始粗晶晶粒由等轴晶变成片层晶,且发生明显细化,6道次后晶粒片层厚度由退火态的~50μm细化到0.2μm左右;晶粒细化主要以位错滑移分割为主,并伴随少量的孪生;材料的硬度和屈服强度明显提高,9道次后达到最大值,硬度为137HV,约为母材的3倍;屈服强度达450MPa,约为母材的5倍;断裂延伸率在首道次剧烈下降,并在随后道次保持在5%左右。
This work at room temperature using the cumulative roll-rolling process of pure copper sheet 1 to 9 times the plastic deformation of large plastic processing. Microstructure evolution and mechanical property evolution of the pure copper plate during the process of accumulative rolling were obtained by using the optical microscope and the dual-beam system FIB / SEM, TEM and tensile testing machine to observe the microstructure and mechanical properties. The results show that there are some defects such as micro-cracks and nanostructures in the initial interface formed by cumulative overlap rolling, in which the micro-cracks gradually disappear with the rolling process and eventually form the metallurgical interface. The nanostructures consist of sheets with 20-60 nm Stratum composition, and includes deformation twins. Under the combined action of compressive force and shearing force of the roll, the original coarse grain changed from equiaxed grain to lamellar grain and remarkably refined. After 6 passes, the thickness of lamellae was reduced from ~ 50μm in annealed state To about 0.2μm. The grain refinement is mainly dominated by dislocation and slip splitting with a small amount of twins. The hardness and yield strength of the material are obviously increased, reaching the maximum value after 9 passes, the hardness is 137HV, 3 times the yield strength; yield strength of 450 MPa, about 5 times the base metal; elongation at break in the first pass dropped sharply, and in the subsequent pass to maintain at about 5%.